1. Field of the Invention
The present invention relates to an improved, foot operated electrical control that has an easy-to-assemble set of operating components including an electrical switch and a variable resistance potentiometer that are carried by a pair of operating arms that, in turn, are mounted for relative pivotal movement on a common mounting shaft that also pivotally connects a base and treadle-type cover that cooperate to protectively house the operating components. More particularly, the present invention relates to a foot operated electrical control of the type just described having an electrical switch and a variable resistance potentiometer that are mounted on separate, relatively movable operating arms, with the switch being arranged to be operated at a time before a control shaft of the potentiometer is begun to be rotated in response to depression by one's foot of the treadle-type cover to cause the treadle to move relative to the base from a normal, "non-operated" position to within a range of "operated" positions.
2. Prior Art
Foot operated electrical controls that include a switch and a variable resistance potentiometer for controlling operation of such equipment as power sources for TIG and MIG types of welding equipment and the like, are well known, and are available for commercial purchase as stand-alone products from a variety of sources.
One such control can be purchased with an electrical switch of either the "momentary" or "maintained" contact type, and with one of a selection of variable resistance potentiometers that have ranges extending from as small as a zero to fifty Ohms, to as large as zero to five MegOhms. However this commercially available control has a number of drawbacks which have long presented a need for improvement.
One drawback of the aforementioned control is that its switch actuates at a time after its potentiometer shaft has begun to rotate in response to downward foot pressure on a treadle-type cover of the unit--whereby some of the so-called "lower end" range of resistance of the potentiometer is "lost," which can cause welding equipment or other equipment that is controlled by the unit to be inoperable within a desirable "lower end" of its range of performance.
Another drawback of the aforementioned control is that all but one of its several operating components are mounted (typically by threaded fastener connections) to the base of the unit, with the unit's only operating arm being separately connected to a mounting shaft that pivotally connects the treadle-type cover to the base--an arrangement that necessitates careful positioning during assembly of the switch and the potentiometer so that these operating components will be properly engaged and operated by separate formations of the operating arm when the operating arm is moved out of its normal "non-operated" position in response to depression of the treadle-type cover by the foot of an operator.
Another drawback of the aforementioned control is that a gear rack that is carried by the single operating arm, and a pinion that is mounted on an operating shaft of the potentiometer (a pinion that is rotated by the gear rack when the single operating arm is moved relative to the base) are positioned relatively "openly" and "exposed" within the relatively large confines of a generally rectangular housing that is cooperatively defined by the base and by the treadle-type cover--a non-sealed enclosure within which dust and particulate from welding environments and the like tend to collect, the presence of which can cause the operation and the operating life of the gear rack and/or the pinion to be unsatisfactory.
Still another drawback of the aforementioned control is that it utilizes a single spring that is interposed between the base and the treadle-type cover to bias the treadle upwardly away from the base toward a "non-operated" position, and to thereby effectively bias the treadle-engaged operating arm toward its "off" position wherein the operating arm does not actuate the switch--a spring that, if broken, permits the treadle to drop under the influence of gravity to actuate the switch and to rotate the potentiometer control shaft toward its so-called "high end" resistance setting which, in turn, tends to fully power control-connected equipment such as the power supply of a welder. The possibility that a broken spring of the control may cause fullest power operation of connected equipment presents a safety concern.